1. Technical Field of the Invention
The invention is related to the field of thermal switches for selectively providing a low thermal impedance path.
2. Background of the Related Art
It is sometimes desirable to provide selective heat flow between two points, by use of a thermal switch. Such thermal switches ideally involve a large difference in thermal impedance between when the switch is “on” (low thermal impedance desired) and when the switch is “off” (high thermal impedance desired). Also, it will be appreciated that it would be desirable for such switches to be reliable, light in weight, low in complexity, and require no additional external power for activation.
A concentric thermal switch based on the principle of differential radial thermal contraction is described in Binneberg et al., U.S. Pat. No. 6,305,174. However the device of Binneberg meets only one of the above criteria, failing to provide a high redundant impedance in the “off” state due to heat leaks through the small spacers used to maintain a gap between the concentric bodies.
Another prior art device is that descried in Marland et al., U.S. Pat. No. 6,276,144. The device described in Marland employs the principle of axial thermal contraction to cause switch engagement. Though referred to as a thermal switch, this device is actually a thermostat that does not provide the necessary directionality to enable selective coupling to one of a pair of heat sinks.
From the foregoing it will be appreciated that there is room for improvements in thermal switches.